The present invention relates to a device for cooling and heating a urea solution. More particularly, the present invention relates to a device for cooling and heating a urea solution for a construction machine, and a control method therefor, which are configured to reduce nitrogen, oxides in exhaust gas discharged from an engine.
According to Tier-4 final emissions regulations for diesel engines in 2014, in order to reduce more nitrogen oxides in exhaust gas through an exhaust pipe, a urea injector mounted on the exhaust pipe receives the urea solution of the urea solution tank by a urea solution pump and injects the urea solution into the exhaust gas,
Thus, the nitrogen oxides are converted into N2 and H2O by catalysis between the urea solution and a selective catalytic reduction (SCR) catalyst, thereby reducing the nitrogen oxides (NOx) in the exhaust gas.
On the other hand, since the urea solution contains much water and the freezing point thereof is −11° C., when the temperature of outside air is low, the urea solution in the urea solution tank is heated to an appropriate temperature before the urea solution tank supplies the urea solution to the urea injector.
When the temperature of the urea solution supplied to the urea injector from the urea solution tank is higher than a set temperature, components of the urea solution vaporize and emit odor. In addition, since chemical reaction occurs and irreversible chemical derivatives are generated due to the vaporization of the area solution, corrosion occurs which affects the durability of related parts such as the urea solution pump.
In contrast, when, the temperature of the urea solution supplied to the urea injector is lower than the set temperature, the urea solution solidifies such that the urea injector is not capable of injecting the urea solution into the exhaust pipe effectively.
In addition, in contract to a truck that moves fast so a urea solution tank thereof is easily cooled by outside air, construction machines such as an excavator operate at the same place or operate while slowly moving so cooling a urea solution tank thereof is not easy.
Furthermore, hot air due to heat exchange with an engine or a hydraulic component of construction machines affects the urea solution tank such that a temperature of a urea solution in the urea solution tank is increased. When such an increased temperature of the urea solution is detected, an error message is delivered to an operator, and then after a predetermined time elapses, the machine is switched into protection, mode to not be operated.
Therefore, workability decreases since the machine does not operate until, the temperature of the urea solution in the urea solution tank falls bellows a preset temperature.
Accordingly, it is desirable to provide a device for cooling and heating a urea solution for a construction machine, the device being configured to maintain the urea solution of a area solution tank at an appropriate temperature since the device maintains the urea solution at the appropriate temperature so an operation of a construction machine can be continuous, thereby improving workability of the construction machine.
In accordance with an aspect of the present invention, a device for cooling and heating a urea solution for a construction machine according to an embodiment of the present invention includes: an engine including a cooling fan, a coolant pump, and a main cooler;
a urea solution tank storing the urea solution and provided with an embedded heat exchange pipe through which first coolant or second coolant circulates;
an additional coolant tank storing the second coolant cooling the urea solution stored in the urea solution tank;
a water pump supplying the second coolant from the additional coolant tank to the heat exchange pipe;
a valve configured to be opened or closed in order to supply the first coolant by driving of the coolant pump and the second coolant of the additional coolant tank by driving of the water pump to the heat exchange pipe of the urea solution tank through a supply line, and in order to move the first coolant and the second coolant, which are heat-exchanged at the heat exchange pipe of the urea solution tank, to the coolant pump and to the additional coolant tank, respectively; and
a controller outputting drive signals to a driver of the water pump in order to supply the second coolant of the additional coolant tank by the water pump through the valve and the supply line when a temperature of the urea solution in the urea solution tank exceeds a set temperature and to a driver of the coolant pump in order to supply the first coolant by the coolant pump to the heat exchange pipe of the urea solution tank through the valve and the supply line when the temperature of the urea solution in the urea solution tank is equal to or lower than the set temperature, and opening or closing the valve.
In accordance with an aspect of the present invention, a control method of a device for cooling and heating a urea solution for a construction machine according to another embodiment of the present invention, wherein the device includes: an engine including a cooling fan, a coolant pump, and a main cooler;
a urea solution tank storing the urea solution and provided with an embedded heat exchange pipe through which first coolant or second coolant circulates;
an additional coolant tank storing the second coolant cooling the urea solution stored in the urea solution tank;
a water pump supplying the second coolant from the additional coolant tank to the heat exchange pipe;
an extra cooler dissipating heat of the second coolant; discharged alter heat exchange with the urea solution of the urea solution tank, by heat exchange with outside air;
a temperature sensor detecting a temperature of the urea solution in the urea solution tank;
a first valve configured to supply the second coolant of the additional coolant tank to the heat exchange pipe of the urea solution tank through the supply line;
a second valve configured to supply the first coolant to the heat exchange pipe of the urea solution tank through the supply line;
a third valve configured to discharge the first coolant and the second coolant from the heat exchange pipe of the urea solution tank-through the discharge line after heat, exchange with the urea solution contained therein; and
a controller receiving a detection signal of the urea solution in the urea solution tank which is detected by the temperature sensor,.wherein the control method includes:
checking a closed state of the first-valve, the second valve, and the third valve and an OFF state of the water pump;
determining whether the temperature of the urea solution in the urea solution tank detected by the temperature sensor exceeds a set temperature; and
opening the first valve and closing the second valve and third valve so as to supply the second coolant of the additional coolant tank to the heat exchange pipe of the urea solution tank through the first valve and the supply line and so as to move the second coolant having exchanged heat with the urea solution of the urea solution tank to the extra cooler through the discharge line when the detected temperature of the urea solution exceeds the set temperature.
According to an aspect of the present invention having above-mentioned construction, the device for cooling and heating the urea solution for the construction machine is configured to maintain the urea solution of the urea solution tank at the appropriate temperature in order to reduce the nitrogen oxides in the exhaust gas, thereby preventing the urea solution from evaporating or degenerating. In addition, the device is configured according to an aspect thereof to inject the urea solution into the exhaust pipe smoothly, thereby reducing nitrogen oxides, and the device is configured to ensure an expensive construction machine can operate continually, thereby improving workability of the machine.